Efficacy and safety of fecal microbiota transplant in irritable bowel syndrome: An update based on meta‐analysis of randomized control trials

Abstract Background and Aims Fecal microbiota transfer (FMT) is a potential treatment for irritable bowel syndrome (IBS). Several randomized trials have tested FMT effects using different routes of administration, doses, and sample sizes. We aim to assess the overall efficacy of FMT for IBS patients and the safety of the intervention. Methods We systematically searched four databases for randomized control trials that studied the efficacy and safety of FMT in IBS patients. Results We included 8 randomized trials (472 patients) that compared FMT with placebo in IBS patients. Pooled results showed no statistically significant difference between FMT and control groups in the overall change in IBS symptom severity (IBS‐SSS) at 1 month (p = 0.94), 3/4 months (p = 0.82), and at the end of trials (p = 0.67). No significant difference in the total number of respondents between the FMT and control groups (risk ratios = 1.84, [95% confidence interval (CI) = 0.82–2.65], p = 0.19). Although the oral route of administration showed a significant difference in the number of respondents (p = 0.004), there was no statistically significant difference in the IBS‐SSS when subgrouping the oral route of administration (mean difference = 47.57, [95% CI = −8.74–103.87], p = 0.10). Conclusion FMT is not an effective treatment to relieve all the symptoms of IBS. Even in the groups that showed relatively significant improvement after FMT, the effect was proven to wear off over time and the re‐administration carries a low success rate. Future research should consider different bacterial‐based interventions such as probiotics or specific antibiotics.


| INTRODUCTION
Irritable bowel syndrome (IBS) is a chronic multifactorial functional gastrointestinal disorder, that develops in the middle or lower parts of the gastrointestinal tract (GIT). 1,2 It is a symptom-based disorder that is currently clinically diagnosed by Rome criteria. 3,4 Rome III and Rome IV criteria resulted in more specific diagnosis and lower prevalence rates of IBS. 5,6 Rome IV is the last update that was released in May 2016, one of the main modifications to the Rome III criteria is that discomfort is no longer accounted for and abdominal pain is now mandatory for diagnosis, also symptom frequency to be at least once per week. 6 IBS presents with many symptoms that include abdominal distention, bloating, and pain, as well as altered bowel habits. 3,7 According to the symptom presentation, IBS is classified into three subtypes; IBS with diarrhea (IBS-D), IBS with constipation (IBS-C), and IBS with mixed bowel pattern (IBS-M). 8 Most recent studies suggest that the worldwide prevalence of IBS currently ranges between 4% and 10%, with the lowest prevalence rates in Singapore, and the highest prevalence rates in Egypt. It is also shown that the prevalence of IBS is higher in women than in men. Regarding age, studies have shown that IBS is more common among adults, and as age increases the prevalence of IBS decreases. 5,6,9,10 IBS patients are more likely to suffer from depression and lower quality of life (QOL), the incidence of depression co-occurrence in IBS patients is estimated to be between 44% and 84%. 11 Although the exact etiology of IBS is still unknown, studies suggest that multiple factors including inflammatory agents, visceral hypersensitivity, genetic factors, disorders in gut-brain interaction, and psychosocial stress, all contribute to the pathogenesis of IBS. [7][8][9] Consequently, there is an imbalance in the gut microbiota, which is known as dysbiosis, which results in a disturbance of the integrity of the mucosal epithelium as well as GIT motility. 12,13 Recent research studies on gut microbiome-focused treatment for IBS explore the manipulation of gut microbiota by prebiotics, probiotics, antibiotics, dietary changes, and fecal microbiota transfer (FMT). 14 In this review, we focus on FMT. FMT is a novel treatment to restore the balance of gut microbiota through the transfer of fecal microbiota of a healthy donor into the patient's GIT via either oral capsules, nasojejunal, or endoscope. 15 It has proved efficacy in the treatment of many GIT disorders, mainly recurrent clostridium difficile infection, in addition to inflammatory bowel disease, hepatic encephalopathy, chronic constipation, and colorectal cancer with mild and self-limited adverse effects. 16 Other extradigestive clinical implications for FMT such as diabetes and obesity are showing promising results for future application. 17 Although it is a cost-effective and readily available treatment option, 18 previously published clinical trials showed conflicting results in symptoms improvement in IBS patients and improving QOL. 2,19 There was a noticeable difference among the clinical trials in the outcome measurement, patient baseline characteristics, and the dose, preparation, and route of administration of FMT. So the aim of this meta-analysis is to compare the efficacy of FMT with placebo through pooling the improvement in the symptom severity score (SSS) and QOL.
We would also assess the safety of the procedure and if there are any associated serious adverse effects. Our study also aims to provide a better quality of evidence from the previous meta-analyses by including only RCTs and excluding nonpeer-reviewed reports.

| MATERIALS AND METHODS
The guidelines of the Cochrane handbook of systematic reviews were followed during the conduction of this review. 20 In addition to the regulations of preferred reporting items of systematic reviews and meta-analysis (The PRISMA 2020 update). 21,22

| Search strategy
We used MeSH terms to form the following search strategy (("irritable bowel syndrome") OR ("irritable" AND "bowel" AND "syndrome") OR ("IBS")) AND (("fecal microbiota transplantation") OR ("fecal microbiota transplant") OR ("faecal microbiota transplantation") OR ("faecal microbiota transplant") OR ("feacal" AND "microbiota" AND "transplant") OR ("fecal" AND "microbiota" AND "transplant") OR ("FMT")) to search four databases: PubMed, SCOPUS (Title and abstract  Outcome: Change in IBS symptoms severity and disease control, also the safety and side effects of the intervention. We excluded case reports, conference abstracts, and single-arm trials. We have gone through two steps to select the eligible studies, (1) title and abstract screening and (2) full-text screening; authors were grouped into two groups and each group performed the screening and data collection separately. The leader author resolved the disputes and compared the results from the two groups. The first and second authors were primarily responsible for data analysis and writing.

| Data extraction
We extracted the data from the included studies in two Excel sheets, in the first one, two authors extracted baseline characteristics of the eligible patients: age, BMI, sex, years since the diagnosis, type of IBS, and so forth, and the other contained outcomes measurement, we divided the main outcomes into (a) primary outcomes: Change from baseline in IBS symptom severity score at 1, 3-4 months, and at the time of last assessment (mean/ standard deviation [SD]); total number of patients who achieved 50 or more points decrease in IBS-SSS; (b) secondary outcomes: QOL score (mean/SD); adverse events such as nausea, abdominal pain, diarrhea, constipation, and bloating. And after finishing the task every two authors revised the other two authors' work; S. A.
N. and Y. H. A. revised the entire work.

| Risk of bias assessment
We used the Cochrane tool to assess the risk of bias in randomized trials (ROB 1), as described in Chapter 8.5. of the Cochrane book depending on the following items: random sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective reporting and other bias (missing protocol or funding issues would be considered as a source of risk), each item was graded as high risk, low risk, or unclear risk of bias.

| Data analysis
We used the Review Manager Software version 5.3 to perform the meta-analysis; the continuous outcomes were measured as mean difference (MD) and SD, and the dichotomous outcomes as risk ratios (RR) with a 95% confidence interval (CI). In case of heterogeneity (χ 2 p < 0.1), a random effect model was adopted, otherwise, a fixedeffect model was employed, and we used "take one out" method to resolve the heterogeneity, in general; the results were considered significant if the p-value was less than 0.05.  Figure 1).  The effect on QoL is significant at six months, but not maintained at twelve months. - The effect on fatigue is significant at six, but not at three and twelve months.  Table 1.
The risk of bias assessment revealed that the included studies were at low risk of bias. A summary of the risk of bias assessment domains is shown in Figure 2. (4) Constipation The pooled results showed that FMT is associated with more constipation compared to the control groups (RR = 5.77, [95% CI = 1.63-20.42], p = 0.007). We observed no significant heterogeneity (p = 0.14, I² = 48%) ( Figure 6).

| DISCUSSION
The results of our meta-analysis showed that there is no statistically percentage after 1 year to 55% and21%. 23,24 This indicates that the beneficial effect of FMT decays over time.
Our results dispute with the results of the previous metaanalyses by Ianiro et al. 30 and Xu et al. 29 In the study by Xu et al.,29 they reported that a single dose introduced by colonoscopy and the nasojejunal tube is more effective than multiple oral doses. We did a subgroup analysis on both methods and found no significant improvement in IBS symptoms in either of them (Supporting Information: File 2, Figure 1). Similarly, in the study by Ianiro et al., they showed a significant improvement in the use of colonoscopy and nasojejunal tube. Interestingly, they found that oral placebo capsules were more significant than oral FMT. 30 This conflict in F I G U R E 5 Forest plots of number of patients who achieved more than or equal to 50 points decrease in (IBS-SSS) score and diarrhea ABDELGHAFAR ET AL. results is mainly due to the different assessment methods used. They used dichotomous data for response or no response to FMT, which is of lower significance than SSS because it does not specify the different degrees of patients' responses. Xu et al. 29 also included a study published as a conference abstract, which is of low quality of evidence and carries a higher risk of bias.
Also, we believe that our report provides better evidence compared to the recently published study by Wu et al. 31 which showed conflicting results with ours. First, they performed an overall analysis of the adverse events related to FMT, which showed no significant increase compared to placebo, while we performed our analysis on each adverse effect separately and found a significant increase in abdominal pain and constipation in FMT compared to placebo. They combined the adverse events in one outcome, which is misleading because adverse events differ in degree of significance and severity. Second, after a subgroup analysis on the route of administration of FMT, they reported that colonoscopy was associated with a more improvement in the global symptoms of IBS compared to placebo, while the oral route was inferior to placebo.
We used the IBS-SSS, which is a more reliable assessment score than the global symptoms score, in our subgroup analysis and found that the oral route is associated with more improvement compared to placebo, while colonoscopy was inferior to placebo. Third, we included more clinical trials, which further validates our results. Another promising therapy is the stem cell-based gut-on-a-chip.
It creates a microenvironment for testing potential therapies and customizing them for each patient. 36 Using antibiotics that are poorly absorbed from GIT like rifaximin and neomycin is now used more widely, but its main flaw is the lack of specificity as it may affect the harmless flora as well. 37 Now, precision antimicrobial peptides called selectively targeted antimicrobial peptides were developed to target certain species without affecting the normal flora. This therapy was only used in dental caries, but in the future, it can be effective in IBS as well. 38 Another similar technique is using the contractile nanotubes produced by certain bacteria that can attach to certain receptors on the cell wall of other bacteria and kill them. We can target certain pathogenic bacteria by modulating those contractile tubes to make them attach to the surface receptor of the pathogenic bacteria. 39 Diet is another important modifiable element in the pathogenesis of IBS. The two main proven dietary plans are eating low fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FOD-MAP) and gluten-free food. 40 FODMAPs are short-chain carbohydrates that are poorly absorbed from the intestinal lumen. They have highly osmotic power, so they increase bloating and abdominal pain.
They are also easily fermentable by intestinal flora with gas production which increases the feeling of boating. 41  The main strength points of our study are as follows: first, we are the first meta-analysis to plot the degree of improvement in symptoms by using symptom severity score as a scaling system, unlike the previous meta-analyses which plotted the improvement of patients as dichotomous data that does not show the degree of improvement in these patients. Second, we included RCT only and unlike the previous meta-analysis, we did not include single-arm trials and conference abstract, which increases the impact of our study.
Third, we did a precise screening for all databases present and included all eligible studies. We also assessed the risk of bias for all included studies and it was generally low, which increases the quality of evidence in our study. However, our study was limited by the significant heterogeneity found in most of the results outcomes and that heterogeneity mostly could not be resolved by the normal statistical ways, which implies that our results are not biologically plausible. Our systematic review was not registered. However, we described our methodology precisely and provided a PRISMA checklist and justified the authors' assessment of the risk of bias.
Moreover, we could not analyze some of the outcomes because they were not assessed in all the included trials.
In conclusion, FMT is not an effective treatment for IBS symptoms whether it is administered orally, by colonoscopy,